2O C. M. CHILD. 



the early embryonic development occurring in gonophores on the 

 hydroid. Planuke of this species were obtained by keeping the 

 gonophore-bearing hydroids in the laboratory for a few days and 

 earlier stages, by opening the gonophores. The development of 

 Phialidium and Gonothyraa was followed through the transforma- 

 tion of planula into hydroid stage, that of Stomotoca only to the 

 late planula. Phialidium and GonotJiyrcea give rise to campanu- 

 larian hydroids ; Stomotoca is an anthomedusa. 



The axial physiological gradients in eggs and developmental 

 stages were demonstrated as susceptibility gradients by disintegra- 

 tion or cytolysis in KCN in indicated concentrations, w/ioo to 

 771/500 in sea water, HgCL in indicated concentrations, w/5o,ooo 

 to w/5oo,ooo in sea water, methylene blue and neutral red in low 

 concentrations in sea water; second, as gradients in rate and 

 amount of reduction of KMnO 4 in various low concentrations in 

 sea water and in rate of reduction of methylene blue; third, as 

 gradients in rate of penetration of the vital dyes, neutral red and 

 methylene blue. The concentrations of agents used are given as 

 " indicated concentrations " because the normal medium sea water 

 is used as solvent in all cases and the concentration given is merely 

 that indicated by the amount of the agent which is added to a cer- 

 tain volume of sea water. As regards KMnO 4 and the vital dyes, 

 the same results are obtained with a wide range of concentrations 

 because these substances are taken up from very low concentrations 

 and accumulate in unchanged or reduced form in the protoplasm. 

 The point of chief importance is that the concentration be low 

 enough so that the staining or disintegration by the dyes and the 

 reduction of KMnO., shall not occur so rapidly as to obscure the 

 differences at different levels. 



A KMnO., solution, indicated concentration 7n/i,ooo, served as 

 stock solution and was diluted two to five times or even more for 

 use in demonstrating differences in rate of reduction. Frequently 

 a drop or two of the stock solution was added from time to time 

 as reduction decreased the concentration. Very low concentra- 

 tions of KMnO., e.g., below w/io,ooo, produce more or less cytoly- 

 sis and can be used like other cytolytic agents to demonstrate the 

 gradients. Special attention may be called to the fact that the 

 permanganate gradient is not simply a gradient in the rate of re- 



